Postage cancellation machines, such as the one described in the U.S. Pat. No. 3,027,830, have been utilized for many years by postal authorities to print a cancellation mark on top of stamps attached to mailpieces. Typically, the cancellation mark is applied by bringing an inked cancellation die into contact with the stamps. The ink cancellation mark provides a visual indication that the stamps have already been used to pay for postage and thus cannot be used again on a subsequent mailpiece. In operation, the cancellation machine utilizes photoelectric scanning devices to detect postage stamps having phosphorescent material or fluorescent material incorporated therein. That is, the photoelectric scanning devices illuminate the luminescent material in the stamp so that, in turn, the luminescent material emits light back to the photoelectric scanning devices. The presence of stamps is indicated if the photoelectric scanning devices sense the light emitted by the stamp. If a stamp is detected, the mailpiece is transported to the cancellation die where the cancellation mark is applied in a known manner.
In prior art cancellation machines however, the ability to automatically separate, transport, and cancel stamps on individual pieces of mail from a stack of "mixed mail" could not effectively be accomplished. The term "mixed mail" is used herein to mean sets of intermixed mailpieces of varying size (postcards to 9" by 12" flats), thickness, and weight. In addition, the term "mixed mail" also includes stepped mail (i.e. an envelope containing therein an insert which is smaller than the envelope to create a step in the envelope), tab and untabbed mail products, and mailpieces made from different substrates. It was found that when attempting to automatically process sets of mixed mail through the cancellation machine, the mail often stalled in transport or double pieces of mail were transported together instead of individual mailpieces. Thus, it was not possible to effectively and reliably separate the individual pieces of mail on a consistent basis in order to ensure that a cancellation mark was placed on each individual mailpiece. Accordingly, it was typical to process stacks of the same size of mailpieces through the cancellation machine and to print the cancellation mark on these same size mailpieces. Naturally, to cancel mail in this manner required a great deal of human intervention since the incoming mailpieces had to be sorted by size and stacked in the cancellation machine for processing with other mailpieces of the same size.